(a) Field of the Invention
The present invention relates to a polyolefin pellet for preparing a fiber, and a fiber comprising the same. More specifically, the present invention relates to a polyolefin pellet that exhibits a high molecular weight and narrow molecular weight distribution, but has high tenacity and an excellent drawing characteristic and can be highly oriented since gel formation is reduced, and the present invention can be applied to various industrial products due to a high draw ratio and crystallinity during a multifilament operation using the same.
(b) Description of the Related Art
Methods for preparing high tenacity fiber polymer are largely divided into two methods, that is, a method of synthesizing new polymer material having a rigid molecular structure and liquid crystal spinning, and a method of reorganizing the existing widely used polymer material consisting of flexible molecular chains by spreading the polymer chains in a drawn direction as possible such that tenacity can be maximally exerted.
Among them, the latter method is being used for high density polyethylene for preparing high tenacity fiber such as a rope, a fishing net, etc.
For reference, high density polyethylene(HDPE) can be produced at low temperature and pressure unlike the existing low density polyethylene, and refers to polyethylene having a density of 0.94 g/cm3 or more. The molecular weight of the high density polyethylene may be distributed from a few thousands to a few millions. Not only the physical properties of the high density polyethylene such as impact resistance, tear strength, environmental stress crack resistance, elongation, etc., but also the processibility such as melt viscosity vary according to the molecular weight, molecular weight distribution and density, etc. Thus, it is required to appropriately control these properties according to the application and utilization range of the high density polyethylene.
Meanwhile, it is known that the mechanical properties of fiber products are more excellent as the molecular weight distribution of high density polyethylene is narrower. That is, if the molecular weight distribution of high density polyethylene is narrow, it has a high draw ratio property, and may have high tenacity due to high drawing. However, if the molecular weight distribution of high density polyethylene is too narrow, processibility may be deteriorated. For example, although high density polyethylene prepared using a common Ziegler-Natta catalyst, chromium catalyst, etc. has excellent processibility, high orientation and drawing are limited and the tenacity is low, and although high density polyethylene prepared using a common metallocene catalyst can be highly oriented and drawn, has molecular weight distribution of 3 or less, and thus, has excellent tenacity, it has poor processibility.
Accordingly, studies on high tenacity fiber products with a narrow molecular weight and improved processibility are required.